Add sliced shallots and ¼ cup of vegetable oil to a small skillet set on low heat (it is imperative that you add the shallots to cold oil lest they burn before crisping up). Stirring constantly, cook shallots until they are golden brown and crispy. With a slotted spoon, transfer fried shallots to a paper towel-lined plate; set aside.

Add enough oil to a medium saucepan so that it comes up about 2 inches high. Place pot on medium-high heat. Once oil is hot, gently drop hard-boiled eggs into it. Stir eggs around to ensure even browning. Once egg exteriors are thoroughly browned, fish them out with a slotted spoon, slice them in half with a serrated knife, and arrange halved eggs on a serving platter.

Discard oil from the skillet in which you fried the shallots and set the skillet on medium heat. Add sugar, fish sauce, tamarind, and water to it; bring mixture to a gentle boil, stirring constantly. Once sugar has fully dissolved, check for consistency. The sauce should have the consistency of maple syrup. If at this point the sauce is still too thin, reduce it a bit more. If it is too thick, add a little more water to thin it out. Once you have the desired consistency, remove skillet from heat and pour sauce over prepared eggs.

Sprinkle fried shallots over the top of the eggs. Garnish with red pepper slivers and cilantro leaves. Serve son-in-law eggs with steamed jasmine rice.